The present disclosure relates generally to systems and methods for neurostimulation and neural recording and, more particularly, to systems and methods for operating a microstimulator with charge-balancing techniques for biomedical implants and instrumentation.
The use of electrical microstimulation to manipulate neuronal circuits has been studied for many years. Techniques related to electrical microstimulation enable a wide variety of biomedical applications including neuroprosthetics to restore motor and sensory function, neurorepair to aid rehabilitation from brain injuries, and neurotherapeutics to treat nervous system disorders. A recent trend is to develop new technologies that can perform closed-loop microstimulation at a large-scale. There are multiple challenges to obtaining neuro-feedback while stimulating, and work continues on lessening residual voltage and stimulation artifacts.
Conventional stimulator designs use discrete components to achieve high-voltage compliance and high output impedance. However, such stimulators, which are bulky, have low-channel-count, and have high power consumption, are not suitable for implantable devices. Custom system-on-chip (SoC) stimulators often employ a feedback-assisted current mirror structure and high voltage process. However, these systems present a large chip area that is undesirable for implantation. Some systems use off-chip DC blocking capacitors instead of efficient charge-balancing mechanisms. As a result, these systems often have poor channel density and are difficult to be integrated into large-scale stimulator implants.
Prior high-channel stimulator SoCs with tens to hundreds of channels trade off channel density for performance by using a simple cascode current mirror structure, which cannot offer sufficient output impedance. They also lack mechanisms to actively monitor residual charge and ensure charge-balancing in favor of increasing channel count. These stimulators are not suitable for acute microstimulation applications, such as (for example) cortical stimulation and vagus nerve stimulation.
Thus, there is a need for new and refined systems, methods, and architectures for implantable neurostimulators.